Accelerators and particle detectors > How do we detect what's happening? > Detecting the world

Detecting the world

Let's look at the most familiar
example of this source/target/detection scheme:
the way in which we perceive the world.

What we think of as "light" is really made up of
billions and trillions of particles called "photons."
Photons, like all particles, also have
wave characteristics.
For this reason, a
photon carries information about the
physical world because it interacts with what it hit.

For example, imagine that there is a light
bulb behind you, and a tennis ball in front of you.
Photons travel from the light bulb (source),
bounce off the tennis ball (target), and
when these photons hit your eye (detector),
you infer from the direction the photons
came from that there is a round object in front of you.
Moreover, you can tell by the different photon
wavelengths that the object is green and tan.

Our brain analyzes the information, and creates the sense of a "tennis ball"
in our mind. Our mental
model of the tennis ball helps to describe the reality around us.

We use the information of bounced-around
light waves to perceive our world.
Other animals, like dolphins and bats, emit and detect
sound waves. In fact, any kind of
reflected wave can be used to get information about
the surroundings.